1. Field of the Invention
The invention relates to a method for picture-in-picture insertion, in which a sequence of decimated inset pictures is written to a memory with at least two segments and is read out for insertion into a sequence of main pictures, to be precise in accordance with the preamble of claim 1, and also a circuit arrangement for picture-in-picture insertion, in particular for carrying out said method in accordance with the preamble of claim 6.
2. Background Art
Various methods and apparatuses for inserting one or more inset pictures into a main picture (PIP—Picture In Picture) are known. In this case, the inset pictures stored in the memory are read out synchronously with a main picture. Since the read-out speed is generally higher, in a manner corresponding to the decimation of the inset picture, than the write-in speed, a seam can occur in the inset picture on account of the write pointer being overtaken by the read pointer, since the inset picture is then composed of a current part and a preceding part.
In particular in the case where the two parts originate from different motion phases, a disturbing effect is produced since moving objects through which the seam passes are displayed in a distorted manner. Moreover, if the frequencies of the inset and main pictures do not correspond exactly, the seam drifts, which is perceived as particularly unpleasant.
EP 0 739 130 A2 discloses, for the purpose of avoiding this problem, storing two inset pictures (or fields in each case) in the memory device, so that it is always the case that exactly one picture can be read out while the next picture is written. Although this prevents the write pointer from being overtaken by the read pointer, there is nonetheless a significant disadvantage in that the storage capacity must be very high, which is associated with considerable costs.